Questions tagged [key-derivation]

In cryptography, a key derivation function (or KDF) derives one or more secret keys from a secret value such as a master key or other known information such as a password or passphrase using a pseudo-random function. Keyed cryptographic hash functions are popular examples of pseudo-random functions used for key derivation.

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BIP32 Extended Key to EC Private and Public Key Pair

We are working on an application in Android using Java. In our project, we used to generate EC key pairs (of size 384 bits) using SpongyCastle - an old Android version of Bouncy Castle. The problem ...
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Scrypt cipher - known vulnerabilities and cryptanalysis? [duplicate]

there is a Scrypt cipher which is used for exmaple by some cryptos like LItecoin for their mining algorithm. I never heared of scrypt. I know eg SHA256 which is well analyzed and considered as secure ...
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Multiple random keys vs multiple keys derived from master key

If Alice is going to share a symmetric encryption key and a kmac key with Bob using asymmetric encryption (sign with static key, encrypt with ephemeral keys - an authenticated KEM), what are the ...
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Multiple AES Key Derivation from a master key

I need cryptography advice regarding this issue. Kamus is a service that encrypts secrets for applications running on Kubernetes. When using AES (actually, Rijndael) symmetric encryption, Kamus uses ...
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ZKA Approval Scheme

I'm having hard time finding any resources for ZKA (Zentraler Kreditausschuss Approval) security schematics used by IFSF Part 3-21 Security Standard (https://ifsf.org/documents/ifsf-standards/). ...
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“Safe” or Safest Method for Non-Hardened Key Derivation Functionality

I'm currently working on the development of an unorthodox system in which, ideally, there would be one master key pair, with thousands of keys derived from it. There needs to be a way to prove that ...
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Is using AES-256 with a key of less than 256 bits of entropy still quantum-resistant?

Encrypting with AES-256 is widely claimed to be post-quantum secure. But let's take a case where you use an initial key that has less than 256 bits of real entropy. In this example, let's work with a ...
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aeskeygenassist with only one imm8

I'm analyzing a binary which for its AES encryption, its only calling aeskeygenassist once and for the last argument (imm8, the ...
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Why RSA-KEM is more secure than Textbook-RSA?

I am studying RSA-KEM but I can not see why it should be as secure as padding RSA messages (e.g with RSA-OAEP) when exchanging a key between two parties (say A and B). It is easy to see that Textbook-...
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Key-Agreement & Key-Transport for Symmetric Authentication System

Question: I want to know what kind of Master Key sharing process is pursuit on Symmetric encryption environments (strictly symmetric, also in the key sharing scheme). As I am aware there are several ...
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Would XOR'ing two Argon2 keys add extra security?

When a user registers on the app, they need to provide a password they create and we provide them with a randomly generated passphrase (e.g. Apple Cat Ladder Fire). We then use Libsodium's ...
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memory-hard KDF that's just a giant permutation?

Why aren't there memory-hard KDF functions that simply build a 1GB permutation and permute it? Then hash the 1GB result. For example, use a hash function (unfixed output mode) on the key+salt and use ...
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Why use PBKDF2 over SHA-512 to derive AES encryption key? [duplicate]

Suppose I am using user passwords to derive AES-128-CBC encryption key. This key will be used to encrypt some sensitive data for the user so that even the website owner / operator can not decrypt it. ...
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Given a hash function; assuming domain % codomain = 0 and uniform collision distribution; how is entropy lost by collisions (not output truncation)?

Assuming our domain and codomain both have 4 elements, the uniform distribution of inputs to outputs means the function is injective. It is widely agreed that randomly selecting a domain element ...
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Entropy preservation through cryptographic hash function

Background First, while studying MinEntropy a bit, I came across an NIST paper, "DRAFT SP 800-90B (second draft)," which suggests "twice" the entropy of the underlying block of a cryptographic hash ...
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Securely derive AES and ED25519 keys from a ED25519 seed

Go's ed25519 package exposes a function which allows creating a private key from a 32 byte seed. See: https://godoc.org/golang.org/x/crypto/ed25519#NewKeyFromSeed The reason I want to use this is ...
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Is there more than one public key for a private key?

Does deriving the public key from an RSA private key always yield the same result? And if so, does this generally apply to all asymmetric cryptosystems?
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Split hash for 2 keys

These are the steps: Hash ECDH shared secret with SHA3-512 Concatenate odd bytes and rehash with SHA3-512 for AES-256 key Concatenate even bytes and rehash with SHA3-512 for KMAC key Is this key ...
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Key derivation scheme with shared secrets?

I want to derive a list of sub-keys derived[t] from a master key mk by a key derivation function ...
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Are there any known problems or attacks for using SHA1(AES_key) as the HMAC key?

See this answer that explains the following sequence of operations: CipherText = IV|| AES(key1,iv,message) tag = hmac(key2,ciphertext) That answer says, You ...
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Station-to-Station protocol questions

Basic Station-to-Station protocol which authenticates Bob and Alice if they safely shared their long-term asymmetric public keys. Alice sends Bob her public key $A_K$ Bob receives $A_K$ and computes ...
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RSA Modulus doesn't match the primes [closed]

I generated a 2048-bit RSA key with ssh-keygen. When running: openssl rsa -in key -noout -text The result is: ...
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Security implications of using a high entropy password with a low iteration count for a key derivation function

This question is related to my other question, but also this entropy calculation question as well as this article about PBKDF2. It may also be considered as a duplicate of this question, although in ...
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Key derivation on Arduino

The ATmega2560 is slow - it's a single core, 16MHz 8-bit AVR. Despite that, I need to use some encryption on it, and since it is limited to a few blocks, AES-256 can be used. However, the key ...
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Why cryptsetup default KDF is PBKDF2 and not Argon2(id)?

I plan to do a clean install of ArchLinux with Full Disk Encryption (with LUKS) but I'm not sure to understand the default KDF choice (PBKDF2+SHA-256). I didn't manage to find any pieces of evidence ...
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Rekeying procedure - how “far” from bijection?

Imagine that I want to change the key in order to prevent side-channel attacks on key and to protect against big load on the one key. It is desirable that key change procedure would look like random ...
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Optimal memory-hard KDF parameters when faced with small, slow memory

I am developing for a low-power embedded system. It has two ARM9 processors at 48 MHz each. One of the processors has access to 6 MiB of "fast" memory as well as access to 26 MiB of "slow" memory. The ...
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Should we run PBKDF2 for every plaintext to be protected or should we run PBKDF2 only once?

I am going to store secrets from users. The secrets need to be stored confidentially. For this question, I am concerned only with confidentiality (not integrity). Here is how my encryption scheme is: ...
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What is the practical impact of using System.Random which is not cryptographically random?

I recently noticed a .NET software using PBKDF to derive an encryption key from a password string. This password string was ...
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Use a SHA256 as a key for AES256

Is it safe to use the SHA256 of a hard-to-bruteforce string as the key to encrypt data with AES256?
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What is a randomly derived key?

It is a well-known fact that using the same key + nonce combination with a stream cipher twice breaks security. The NaCl library has different primitives for authenticated encryption (i.e., ...
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Are two keys derived from the same password vulnerable to a related key attack?

Background I am currently writing a password manager application. As usual, the passwords are put in a file encrypted using a user-entered password. I'm using the NaCl library but actually it's not ...
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“Dave Check” for a tweakable P-256 ECDH KDF

I have two devices with hardware tokens that contain P-256 private keys, and which allow me to compute ECDH shared secrets with arbitrary public keys. I need to build a tweakable key derivation ...
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Is it safe to reuse the salt for generating symmetric keys for a chat application?

I'm writing a program that allows two users to communicate over E2E encrypted chat with a secret they have agreed upon in the past. The process works as follows: A key is derived from the secret ...
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AES key schedule. Does it use a KDF to generate the round keys?

So for each round in AES a different key is used, and as I saw the keys are created form a master key. My question is how these round keys are generated. Are they created via a Key Derivation ...
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Are two halves of PBKDF output “related” [duplicate]

In other words, in the context of authenticated encryption using Encrypt-Then-MAC, is this stupid?: ...
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ECDHE Key with KDF Necessary [duplicate]

Is it necessary to pass a ECDH generated key to a KDF? According to the python cryptography documentation, it is stated that For most applications the shared_key should be passed to a key ...
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Generating the Backup Exec AES-256 GCM key used to encrypt/decrypt LTO5 tape drive data

I've got an LTO5 tape that was backed up using Backup Exec (BE), which used hardware compression when writing to the tape. I've been given the passphrase that BE used to create the actual encryption ...
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I need to send 16 bytes using ECC keys on a resource-constrained device

I have a system where a resource-constrained device has to send 16 bytes. It has its ECC key pair, and a peer's Public ECC Key. We're using the p256 curve. The device also has an AES-128 hardware ...
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Can you derive a 128 bit AES encryption key using PBKDF2 with SHA-256

I got confused about key derivation functions. For my project, I need to derive a 128 bits AES encryption key in CTR mode. To do so, I'm using a PBKDF2 to derive this encryption key using an initial ...
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Off-Chain Channel With Multi Participants That Have Different View/Write Access

I'm looking to expand my blockchain ability to have off-chain channels between different participants (let's say more than 2 participants). The requirements: Only the participants of the channel ...
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Bluetooth Low Energy: Key generation

I'm studying the BT core spec v5.1 to understand the security features and how everything fits together. I am looking at Secure Connections for now. In the field "Key generation" it says it uses P-...
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Derive operations from an arbitrary number

I don't really know how to phrase this question, so I'll just mention the idea. This is partially reminiscent (at least in spirit to white box crypto): Can one derive arithmetic operations from a ...
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how are variable key sizes produced?

I am current learning the internal working of several Symmetric key Cryptographic algorithms, and came across DES and AES. DES takes in input a 64 bit key and AES-128 takes in input a 128 bit key ...
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Can I use XOR to establish a longer shared secret?

SIKEp434 can only be used to encapsulate a 16 byte (128 bit) shared secret key. Most encryption algorithms these days (specifically (X)ChaCha20) require a 256 bit key to be secure, especially in a ...
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Do you really need a KDF when you have a PRF?

My understanding is that a KDF is like a PRF, except that it has a preliminary step that "extract" entropy. It is thus needed when the entropy is non-uniform (for example the output of ECDH is modulo ...
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Hashing a hash for authentication

I currently use Argon2 to derive a key (I will use a salt which I will save in a file as plaintext for when I later need to derive a key again) from a given password which I will use to encrypt a file ...
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Key Value Based Key Derivation

For a system that is using public key cryptography to authenticate users and their actions I'm trying to solve (ease) UI/UX problem so that users will be able to use login/passwords they're accustomed ...
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Key Derivation Functions vs. Password Hashing Schemes

Key derivation functions, such as HKDF (standardized in RFC 5869), are meant to stretch some initial keying material having enough entropy, like a Diffie-Hellman shared value, into one or more strong ...
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PBKDF and Entropy

We all regularly use password based, key derivation functions, however something that strikes me as counter intuitive is how PBKDF can somehow "stretch" the entropy of a supplied password to generate ...